See also usb_modeswitch package in [community], which you may need in future since in udev-157 modem-modeswitch has been renamed and changed as described in the commit. This package does not need any modifications, just install it.

Also you can create udev's config: /etc/udev/rules.d/15-huawei-e1550.rules

Connecting internet

Now you have new 2 or 3 /dev/ttyUSB* devices.Most likely first of them (ttyUSB0 if you had not such devices before)
is PPP compatible modem. Use it as usual with pppd, kppp, gnome-ppp, network-manager, etc.

Note: If you want to use your 3G modem with network-manager, you have to install the package modemmanager (it's in the extra repository) and then restart the networkmanager (usually /etc/rc.d/networkmanager restart). Now you can 'Enable Mobile Broadband' in your networkmanager applet in GNOME

AT commands

There are some usefull commands:

AT^U2DIAG=0 - the device is only Modem

AT^U2DIAG=1 - device is in modem mode + CD ROM

AT^U2DIAG=255 - the device in modem mode + CD ROM + Card Reader

AT^U2DIAG=256 - the device in modem mode + Card Reader

AT+CPIN=<PIN-CODE> - enter PIN-code

AT+CUSD=1,<PDU-encoded-USSD-code>,15 - USSD request, result can be found (probably) in /dev/ttyUSB2.

USSD Requests

Success Stories

2010-August-03: I didn't do anything, I just installed usb_modeswitch-1.1.3-2 and my kernel is 2.6.33. In the syslog (/var/log/messages.log) the usb_modeswitch can automatically configure the modem correctly but I still cannot connect to the internet using gnome network manager applet, then I installed the modemmanager package and restart the networkmanager service. Everything is working properly now.